Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$41.27	10.644%	$45.6628	$45.66	$45.65	$45.70
Purchase #2	$64.29	12.450%	$72.2941	$72.29	$72.30	$72.30
Purchase #3	$231.75	8.829%	$252.2112	$252.21	$252.20	$252.20
Purchase #4	$110.86	11.630%	$123.753	$123.75	$123.75	$123.80
Purchase #5	$21.64	3.736%	$22.4485	$22.45	$22.45	$22.40
Purchase #6	$111.82	12.300%	$125.5739	$125.57	$125.55	$125.60
Purchase #7	$163.38	13.509%	$185.451	$185.45	$185.45	$185.50
7 purchase totals =	$745.01		$827.3945	$827.38	$827.35	$827.50